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Simultaneous enhancements of strength and toughness by multiscale lamellar structure in Ti_(2)AlNb based intermetallic

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Journal of Materials Science & Technology 2024年第7期174卷 249-261页

作者： Fan Zhang weidong zeng Penghui Zhang Haoyuan Ma Jianwei Xu State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Defense Technologies Innovation Center of precision forging and ring rolling School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China

Multi-scale lamellar structure significantly improves toughness of Ti_(2)AlNb based alloys,which are inher-ently brittle intermetallics,without compromising their *** structure was achieved through-B2-transus-forging(TBTF)combined with O+B2 two-phase region heat *** types of multi-scale lamellar structures were obtained by controlling the cooling rate after *** variations were mainly attributed to differences in the distribution,content,and size of the thick lamellar O phase and the size and crystallographic orientation of B2 *** analyzing the microstructural characteristics and crystallographic orientation near the crack propagation path,it was found that the crack propaga-tion resistance of thick lamellae,sub grain and grain boundaries(GBs)O phase increased sequentially,accompanied by more tortuous crack propagation ***,B2 grains with high misorientation significantly deflected the crack propagation by cleavage ridges between adjoining cleavage ***-tionally,the development of numerous secondary cleavage ridges,resulting from the transition through varying secondary cleavage planes in distinct sub B2 grains,further hindered the quick propagation of *** was clarified that the cleavage planes were dominantly belonging to{110}.These findings pro-vided valuable guidance for the design of damage tolerance strategies for Ti_(2)AlNb-based intermetallics.

关键词： Multiscale lamellae structure Fracture toughness Crack propagation Ti_(2)AlNb-based intermetallic Through-B2-transus-forging

Analysis of crystallographic orientation and morphology of microstructure during hot working for an alpha/beta titanium alloy

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Journal of Materials Science & Technology 2020年第24期59卷 1-13页

作者： Jianwei Xu weidong zeng Dadi Zhou Wei Chen Shengtong He Xiaoyong Zhang State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an710072China Defense Technoloies Innovation Center of Precision Forging and Ring Rolling School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an710072China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China

This work focuses on analysis of microstructure morphology and crystallographic orientation for Ti-17 alloy during hot *** results show that alpha phase and beta phase influence each other and there is a coordinate deformation between *** non-uniform deformation is observed under small deformation *** observing area can be divided into small deformation zone(area L)and large deformation zone(area H).Both alpha and beta phases remain the initial morphology,and they have better capability of coordinate deformation in area L,while coordinate capability is weak in area H in which alpha phase is ***,the Burgers orientation relations are well preserved in area L,but the orientation relations are more or less destroyed in area *** recovery is the main mechanism of beta phase evolution when height reduction is *** contrast,the continuous dynamic recrystallization(CDRX)of beta phase gradually dominates the deformation pattern as the deformation *** uniformly globularized alpha structure is obtained under large deformation *** unsynchronized rotation of alpha phase aroundpole occurs during deformation,which leads to the uniform crystal structure inside the same alpha *** process is an important step of globularization of the lamellar structure.

关键词： Ti-17 alloy Hot working Microstructure evolution Crystallographic orientation

Variant selection, coarsening behavior of α phase and associated tensile properties in an α+β titanium alloy

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Journal of Materials Science & Technology 2022年第4期99卷 101-113页

作者： Lei Lei Qinyang Zhao Cong Wu Yongqing Zhao Shixing Huang Weiju Jia weidong zeng State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China School of Material Science and Engineering Chang’an UniversityXi’an 710064China Northwest Institute for Nonferrous Metal Research Xi’an 710016China

Effect of cooling rates,i.e.,air cooling and furnace cooling,after solution in α+β phase-field on variant selection,coarsening behavior of α phase and microstructure evolution were investigated in α+β TC21 *** textures of primary α(α_(p))and lamellar α(α_(L))in β phase transformation microstructure(β_(t))were analysed separately,and the orientation relationship among α_(p),α_(L) and the parent β phase were *** addition,the influence of the microstructure characteristics on the tensile properties was *** results showed that all parent β grains,despite their different orientations,produced 12 ideal α_(L) variants with the same texture components and interweave to form a basketweave β_(t) structure under the air-cooling *** α_(p) without Burgers orientation relationship(BOR)with β phase exhibited obviously texture component without overlapping theαL texture *** volume fraction of α_(p) in the furnace-cooled sample(about 50%)was higher than that of the air-cooled sample(about 12%),while the size of it slightly increased with decreasing the cooling *** each β grain,the thick α_(L) in the same orientation formed anαcolony.A typical 3 variant colonies which were related to each other were ***,the α_(L) spatial orientation distribution showed more ***,the BOR between α_(p) and β and the same orientation of some α_(L) and the surrounding α_(p) grains resulting in the overlapping of α_(p) texture component and α_(L) texture *** last,the relationship between microstructure and tensile properties was analysed.

关键词： TC21 alloy Crystallographic orientation Texture Variant selection Tensile properties

A new insight into structural complexity in ferroelectric ceramics

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Journal of Advanced Ceramics 2017年第3期6卷 262-268页

作者： weidong zeng Qingning LI Changrong ZHOU Jiwen XU Changlai YUAN Guohua CHEN School of Material Science and Engineering Guilin University of Electronic Technology Guilin 541004 China

The structure of the ferroelectrics has been widely studied in order to pursuing the origin of high electromechanical responses. However, some experiments on structure of ferroelectrics have yielded different results. Here, we report that the controversial phase structure is due to the adaptive diffraction of nanodomains which hides the natural crystal structure, and the electric-field-induced phase transition is that the natural crystal structure reappears due to the coalescent nanodomains or ordering nanodomains by applying a high electric field. The temperature dependence of dielectric constant with different measurement frequencies and X-ray diffraction (XRD) patterns of unpoled, poled, and annealing after poled ceramics in Bi0.5Na0.5TiO3–BaTiO3 (BNT–BT) ceramics authenticate the statement. These results provide a new insight into the origin of structural complexity in ferroelectric ceramics, which is related to the key role of nanodomains.

关键词： crystal structure adaptive diffraction ferroelectricity phase transitions

A novel annealing method to uniformly refine deformed mixed grain microstructure of a solution-treated Ni-based superalloy

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Science China(Technological Sciences) 2021年第8期64卷 1741-1751页

作者： WANG GuanQiang CHEN MingSong LIN YongCheng LI HongBin zeng weidong MA YanYong CAI JinLiang PENG ChengXu ZOU FenYang Light Alloy Research Institute Central South UniversityChangsha410083China School of Mechanical and Electrical Engineering Central South UniversityChangsha410083China State Key Laboratory of High Performance Complex Manufacturing Changsha410083China College of metallurgies and energy North China University of Science and TechnologyTangshan063009China

Increasing static recrystallization(SRX)nucleation rate and decreasing grain growth rate are the main ways to obtain uniform and fine grain microstructure by annealing ***,it is contradictory to raise the SRX nucleation rate and reduce grain growth rate during isothermal annealing *** is because the increase of the SRX nucleation rate needs to raise annealing temperature,while the decline of grain growth rate needs to reduce the annealing *** solve the contradiction,a novel method named cooling recrystallization annealing treatment(CRT)is designed and *** the CRT,the relatively high annealing temperature in the primary stage can promote SRX nucleation,and the gradually decreased annealing temperature can reduce the growth rate of SRX ***,an aged treatment is first carried out to precipitate high content of theδphase before the ***δphases not only provide large numbers of sites for SRX nucleation but also limit the grain growth due to the pinning effect,especially in the primary high-temperature *** results show that the novel method can refine deformed mixed grain microstructure well when the suitable cooling rate,start and final recrystallization annealing temperatures are *** deformed mixed grain can be uniformly refined to an average size of 8.26μm with the route of 900℃×12 h+1020℃→970℃×20 min.

关键词： Ni-based superalloy annealing method refinement mechanism grain uniformity microstructure evolution

Effects of thermal and electrical histories on structure and dielectric behaviors of(Li_(0.5)Nd_(0.5))^(2+)-modified(Bi_(0.5)Na_(0.5))TiO_(3)-BaTiO_(3) ceramics

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Journal of Materiomics 2017年第2期3卷 121-129页

作者： Jiwen Xu Qingning Li Ling Yang weidong zeng Changrong Zhou Changlai Yuan Guohua Chen Guanghui Rao Guangxi Key Laboratory of Information Materials Guilin University of Electronic TechnologyGuilinGuangxi541004China

The effect of thermal and electrical histories on structure and dielectric behaviors is studied using 0.95(Bi_(0.5)Na_(0.5))_(0.97)(Li_(0.5)Nd_(0.5))_(0.03)TiO_(3)-0.05BaTiO_(3)(abbreviated as BNTLN0.03-BT5)ceramic as a selected *** structure change caused by annealing treatment,and pronounced phase transition and domain switching by electrical poling,are observed to occur,*** dielectric constant and its strong frequency dispersion in unpoled samples decrease evidently by electrical poling due to electric field-induced ordered *** high temperature Maxwell-Wagner relaxor behavior vanishes by annealing treatment due to the loss of electrical inhomogeneity with interface charging *** properties are improved evidently by annealing treatment at 900℃,implying a new appropriate method to improve piezoelectric properties.

关键词： Ceramics Dielectric properties Ferroelectricity Piezoelectricity

Dielectric behaviors and relaxor characteristics in Bi_(0.5)Na_(0.5)TiO_(3)-BaTiO_(3) ceramics

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Journal of Advanced Dielectrics 2019年第5期9卷 57-64页

作者： Pei Chen Jun Wang weidong zeng Changrong Zhou Yongsheng Zhang Qingning Li Jiwen Xu Guohua Chen Changlai Yuan Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology Guilin Guangxi 541004P.R.China School of Material Science and Engineering Guilin University of Electronic Technology Guilin Guangxi 541004P.R.China

Microstructure and dielectric behaviors of heating/cooling and bias-field were investigated in lead-free ceramics(1-x)Bi_(0.5)Na_(0.5)TiO_(3)-xBaTiO_(3)(BNT-xBT,x=0,0.02,0.04,0.06,0.08 and 0.10).The relaxor characters and the Vogel–Fulcher law of frequency-dependent dielectric properties were *** dielectric anomalies with pronounced frequency dispersion at Td,a maximum dielectric with variable frequency-dispersion at Tm and a third Maxwell–Wagner-type relaxation over a wide temperature range in high-temperature region were *** significant dielectric thermal hysteresis,low barrier energy,high freezing temperature in heating process and the maximum dielectric tunability appeared in x=0.4 ceramic.

关键词： Bismuth sodium titanate dielectric relaxor Vogel-Fulcher law dielectric tunability

显微组织对TC11合金高温保时疲劳敏感性的影响

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金属学报 2000年第9期36卷 897-901页

作者：周义刚曾卫东西北工业大学材料科学与工程学院西安710072

详细研究了等轴、三态、网篮三种组织对TC11合金(Ti-6.5 Al-3.5Mo-1.5Zr-0.3Si)520℃高温保时疲劳敏感性的影响,结果表明,当在每次循环峰值保时3min时,三种显微组织的 TC11合金均呈现疲劳寿命显著下降,其中等轴组织下降最大,三态组织其... 详细信息

详细研究了等轴、三态、网篮三种组织对TC11合金(Ti-6.5 Al-3.5Mo-1.5Zr-0.3Si)520℃高温保时疲劳敏感性的影响,结果表明,当在每次循环峰值保时3min时,三种显微组织的 TC11合金均呈现疲劳寿命显著下降,其中等轴组织下降最大,三态组织其次,网篮组织最小.SEM和TEM观察显示,等轴和三态组织的保时敏感性是以大量准解理断裂和车辙状平面滑移为其断裂特征,且准解理断裂和平面滑移随等轴α相减少而减少;网篮组织呈现出循环断裂和三维位错网.本文引用位错切过α2颗粒的模型对平面滑移作了解释,应用蠕变机制分析了三种组织对保时疲劳敏感性的影响.

关键词： TC11合金保时疲劳敏感性准解理断裂平面滑移

ARB工艺对TA15板材片层球化的影响规律

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稀有金属材料与工程 2020年第12期49卷 4222-4229页

作者：韩栋赵永庆曾卫东西北工业大学材料学院陕西西安710072 西北有色金属研究院陕西西安710016

作为剧烈塑性变形方法的一种,累积叠轧工艺(accumulative roll bonding,ARB)是一种可将晶粒细化至亚微米级并大幅度提高板材综合性能的方法。通过研究初始α片层组织、道次变形量分配及换向轧制对片层组织球化程度的影响,可获得ARB工艺... 详细信息

作为剧烈塑性变形方法的一种,累积叠轧工艺(accumulative roll bonding,ARB)是一种可将晶粒细化至亚微米级并大幅度提高板材综合性能的方法。通过研究初始α片层组织、道次变形量分配及换向轧制对片层组织球化程度的影响,可获得ARB工艺对TA15板材片层球化的影响规律。结果表明:当初始片层厚度较小及晶界/晶内片层α厚度差异较小时,片层球化更加彻底。道次变形量过大会引起板材温升显著,进而造成晶界及基体片层球化不均匀,而道次变形量过小将导致片层球化不完全,最终影响基体等轴化效果。随着ARB成形过程换向道次的增加,板材各向的均匀程度提升,板材的晶粒尺寸及极差进一步减小,室温拉伸性能显著提高。

关键词： TA15 ARB 片层球化轧制轨迹